The packet transmission network is, for example, the internet or a data transmission network operating according to an internet protocol. However other packet transmission networks are also used, for example ATM networks (Asynchronous Transfer Mode). In an ATM network the data packets are also referred to as cells. The data packets or cells contain routing data, which is used to forward the useful data contained in the data packets, e.g. address data or path or channel details.
The data packets are transmitted on different transmission paths and/or with different delay times via the packet transmission network. The sequence of the data packets must be reset in the receiver for many applications. For these purposes the data packets for example contain a sequence number or a time stamp. Reference should be made in this context for example to the RTP (Real Time Protocol) transmission protocol, which is stipulated in the defacto IETF (Internet Engineering Task Force) standards RFC (Request for Comment) 1889 and RFC 1890. The header of an RTP data packet therefore contains a sequence number and a time stamp among other things, see RFC 1889, clause 5.1.A jitter buffer is used to effect a transmission with acceptable transmission times despite delays and data packet losses. Data packets are stored for a specific time in the jitter buffer, until the system is no longer waiting for an outstanding packet. If the jitter buffer is full, transmission continues even if individual data packets are missing or a repeat transmission is requested. The size of the jitter buffer therefore influences the waiting time for which the transmission is delayed in the event of missing data packets.
Control of the size of the jitter buffer and therefore the waiting time based on the capabilities of an encoder is known from the standard H.323 “Packet based multimedia communications systems” from the ITU-T (International Telecommunication Union—Telecommunication Standardization Sector), clause 6.2.5.